drm/msm/adreno: un-open-code some packets

Small cleanup, lets not open-code bits/bitfields that are properly
defined in the rnndb xml (and therefore have builders in the generated
headers)

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>